1. Field of the Invention
The present invention relates to an engine for a motorcycle having dummy covers for covering at least a part of cylinder heads from the sides, and overhead covers for covering from above and from the sides at least a part of head covers coupled to said cylinder heads.
2. Description of Background Art
Japanese Published Unexamined Patent Application No. 2000-234562 discloses a configuration in which head covers are at least partially covered from above and from the sides by overhead covers in order to enhance the functional beauty of a motorcycle engine and to improve noise proofing. In this configuration, protrusions provided in the head covers are engaged with the overhead covers, the overhead cover being fastened with bolts to the head covers. Bolt heads are arranged to face the outer surface of the overhead covers. Accordingly, the bolts are visible from the outside. To enhance their appearance, bolt heads having a special shape are employed, and an expensive surface treatment including chroming is performed on the bolt heads.
Japanese Published Unexamined Patent Application No. Hei 11-82051 discloses a configuration in which cylinder heads are at least partially covered from the sides by dummy covers having dummy cooling fins in order to enhance the functional beauty of a motorcycle engine. In this configuration, the dummy covers are snap-fit to stays on the cylinder heads and are fastened with bolts to a crankcase in order to increase vibration endurance. As in JP ""562, the bolt heads are exposed to outside; and, in order to be aesthetically pleasing, special material and costly procedures must be employed.
The present invention was conceived in view of such circumstances. An object thereof is to provide dummy and overhead covers for a motorcycle engine which enhance functional beauty but require no specially shaped parts and no costly surface treatment.
To achieve this and other objects, the present invention provides a motorcycle engine having dummy covers for covering from the sides at least a part of cylinder heads, and overhead covers for covering from above and from the sides at least a part of head covers coupled to the cylinder heads. At least one spot of the dummy covers is fastened with bolts to an engine main unit housing the cylinder heads and head covers. A plurality of engaging protrusions disposed in the overhead covers so as to cover the bolts are resiliently engaged with the engine main unit or the dummy covers such that the overhead covers are detachable or attachable.
In the present invention, no specially shaped parts and no special surface treatment are required to enhance functional beauty. Frequently, side dummy covers are made of metal to eliminate heat and/or are provided with dummy cooling fins to enhance functional beauty. Strong support for the dummy covers is thus necessary. In still other configurations, the overhead covers require no dummy cooling, fins or are formed of a lightweight material, such as a synthetic resin. In these cases, it is not necessary to provide strong support for the overhead covers.
In the present invention, at least one spot of the dummy covers is fastened with bolts to the engine main unit, and a plurality of engaging protrusions provided in the overhead covers are resiliently engaged with the engine main unit or the dummy covers so that the overhead covers are detachable or attachable. Thus, the dummy covers and overhead covers can be supported in the engine main unit in any suitable configuration. The bolts for fastening at least one spot of the dummy covers to the engine main unit are covered by the overhead covers. Attractively shaped parts and expensive surface treatments, which would otherwise be required with exposed bolts, are, therefore, unnecessary. Accordingly, material costs can be reduced, while still providing an engine with enhanced functional beauty.
The dummy covers are provided with notches for arranging spark plugs mounted on the cylinder heads, and the overhead covers are formed in a shape to cover the notches from above. Thus, functional beauty can be enhanced. A plurality of engaging protrusions provided in the overhead covers are resiliently engaged with at least either of the cylinder heads and the head covers so as to be detachable or attachable. The overhead covers can be easily detached or attached, allowing maintenance of the spark plugs to be performed easily.
The cylinders of the engine main unit are coupled to the cylinder heads in portions corresponding to the fins closest to the cylinder heads of a plurality of fins provided in the sides of the cylinders aligned in the direction along cylinder axes of the cylinders. At least one recess is provided in the cylinders, and protrusions provided in the dummy covers fit into the recesses. According to this configuration, the dummy covers are supported by the cylinders in the engine main unit, together with fastening with bolts at least one spot thereof to the engine main unit. The dummy covers, which become relatively heavy, can be reliably fixed to the engine main unit. The mutual fitting portions of the dummy covers and the cylinders can be hidden by the fins provided in the cylinders. The mutual fitting of the dummy covers and the cylinders provides for functional beauty of the engine.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.